Changes

* In Somaliland, similar water cellars were observed that were excavated in impermeable stable soil formations – runoff water entered through a small inlet channel. Other tanks are sealed with a 10cm unreinforced cement lining – it seems that 30m3 is the most economical size as the most volume had that doesn't need reinforcement – such tanks cost US$189 or about US$6.3 per m3 of storage (materials only, presumably).

This [http://www.enviro-friendly.com/Tankmasta-Underground-Installation.pdf Underground tank installation manual] by Tankmasta explains all the steps needed to build an underground tank.

* Video: [http://emas.blip.tv/ Large collection of EMAS movies on different subjects.]